Doing a \set through perl DBI ?

Is there a way to do the equivalent of a "\set foo 1" through perl dbi ?

I tried... 

    $dbh->do("\\set foo 1");

and got a syntax error

Of course, I'd also have to be able to access the value of foo once its set.   I'm guessing the usual way ??? (select :foo)

Thanks for any help !